._ POWER CONTROLLER WITH SWITCHED POWER OUTLETS
FIELD OF THE INVENTION
The invention relates generally to reduction of energy consumption in electrical equipment, and more specifically, to automatically enabling and disabling AC power outlets to start-up and shut-down equipment.
BACKGROUND OF THE INVENTION
The invention has particular though not exclusive application to computer systems.
A stand-alone, single-user computer system may consist of a computer and peripherals such as disk drives, scanners, printers or modems.
The peripherals are useful only when the computer is actually operating.
However, each peripheral typically has its own ON-OFF switch and must be started up or shut down separately from the computer itself. Through inadvertence, certain peripherals may be left operating when the computer is shut off, wasting electric power. A conventional power bar with multiple AC
power outlets permits system components to be started and shut down contemporaneously by tripping a single switch mounted on the power bar.
However, it lacks versatility and is usually located on a floor where the power switch is not readily accessible.
Other computer systems may be configured to respond automatically to incoming telephone calls. To reduce energy consumption, it would be desirable that such systems, or at least required components, start-up automatically in response to an incoming call and then shut off automatically when the call has been handled. A conventional power bar is inadequate for such purposes.
In large computer networks, servers or peripherals may be used infrequently. They may be remote from a particular user and manually Z~39053 -starting-up and shutting-down such devices may be inconvenient. Once again, it would be desirable to automate start-up and shut-down functions.
The present specification addresses such problems.
SUMMARY OF THE INVENTION
In one aspect, the invention provides an AC power controller operable with an AC line voltage from an electrical main. The controller may be configured to resemble a conventional power bar. It has a master power outlet and at least one slave power outlet. Means are provided for coupling the power outlets to the electrical main to power the outlets. The coupling means includesa switch which in an open state isolates the slave outlet from the AC line voltage. In a closed state, the AC line voltage is applied through the switch tothe slave outlet. Means are provided to sense current flow from the master power outlet. Control means control the state of the switch in response to sensed current flow. In preferred form, the sensing means indicate the magnitude of the current from the master outlet. When the magnitude exceeds a predetermined turn-on threshold, the switch is placed in its closed state, enabling the slave outlet. When the magnitude of the current drops below a lower turn-off threshold, the switch is placed in its open state, disabling the slave outlet.
In a simple computer system, a user may plug his computer into the master outlet and his peripherals into one or more slave outlets. The power switch of each peripheral is left in an ON state. When the computer is turned on, the operating current it draws from the master outlet is sensed and the slave outlets are enabled, turning the peripherals on. When the computer is shut down, the absence of current flow from master power outlet is sensed and the slave outlets are disabled, shutting down the peripherals. In such applications,operation is comparable to that of a conventional power bar, but the operating state of the computer actually determines the operating states of the peripherals.
21390~3 -In another aspect, the invention provides an adapter that extends the utility of the power controller. The adapter has a plug or other appropriateconnector that mates with the master power outlet to receive the AC line voltage.
It has variable load means for drawing current from the master outlet. It has 5 detection means for detecting a predetermined condition or signal that indicates the need to power up devices for response. Control means respond to detection of the condition or signal by causing the load means to draw sufficient current from the master outlet current that the threshold value necessary to enable the slave power outlets is exceeded. The adapter may itself be powered from the 10 master outlet and may effectively modulate its own operating current to enable or disable the slave outlets in response to sensed conditions or signals. A verysignificant advantage is that operation is largely independent of the nature of the devices operated from the slave outlets.
The power controller and adapter have various applications. The 15 adapter can be configured, for example, to sense telephone ring signals and to power up a computer system or other devices to handle incoming telephone calls. For such purposes the adapter may be conveniently integrated into a system modem. The adapter may alternatively be configured detect a computer' s attempts to communicate with a peripheral along a particular data 20 line and automatically power up the peripheral. The adapter may respond to various triggering signals.
The adapter may also be configured to trigger ~hutting down of devices connected to further reduce energy consumption. The adapter disables the slave outlets by reducing the current it draws from the master outlet. A
25 timer may be used to trigger disabling of the slave outlets after a fixed period of operation. In a computer system operated from the slave outlets that would require early terrnination of longer transactions or that the system remain powered on for a time period corresponding to the longest expected transaction.
213905~
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For telecommunications applications, the adapter may be configured to detect if a system modem goes "on-hook" (h~nging up after a telephone call) or if the modem fails to go "off-hook" (answering a telephone call). Such events are used to trigger shut-down of the slave outlets. If the adapter is configured to detect on-hook and off-hook conditions, communication software used by the computer system may be modified or extended to produce a series of off-hook and on-hook events that uniquely identifies the end of a telecommunication session and an appropriate time to disable the slave outlets. To shut down individual peripherals, data transfer lines unique to a particular peripheral can be monitored for lack of activity. Such alternatives allow a computer system or individual to be powered for periods varying with individual transaction. A
timing function may then control shut down of the slave outlets to allow completion of any incidental operations required.
Other aspects of the invention will be apparent from a description below of preferred embodiments and will be more specifically defined in the appended claims.
DESCRIPTION OF THE DRAWINGS
The invention will be better understood with reference to drawings in which:
fig. 1 is a diagrammatic representation of a computer system and a power controller from which system components are operated;
fig. 2 is an electrical schematic of the power controller;
fig. 3 is a diagrammatic representation of the computer system, the power controller and a call adapter powers the computer system to handle incoming telephone calls;
fig. 4 is an electrical schematic of the call adapter;
fig. 5 is a state diagram outlining the operate states and procedures associated with the call adapter;
fig. 6 is a diagrammatic representation showing how the call adapter can be incorporated into a modem;
fig. 7 is a diagr~mm~tic representation of the power controller 5 and a serial adapter being used to control start-up of a printer in response to operation of a computer;
fig. 8 is an electrical schematic of the serial adapter; and, fig. 9 is a state diagram outlining the operating states and procedures of the serial adapter.
Reference is made to fig. 1 which diagrammatically illustrates a computer system comprising a personal computer 10 and various peripherals including a monitor 12, a disk drive 14, a scanner 16, a printer 18 and a modem 20. These devices require 110 volts AC for normal operation. The operating 15 voltage is provided by a power controller 22 that has multiple power outlets, namely, a master outlet 24 and five slave outlets 26. The computer 10 is plugged into the master outlet 24 and each of the peripherals into one of the slave outlets 26.
The power controller 22 has a power cord 28 and plug 30 that 20 inserts into a conventional outlet of an electrical main to receive an AC line voltage of 110 volts. A fuse 32 prevents overloading of the power controller 22. A manual switch 34 sets three operating states: an OFF state in which no power is supplied to the outlets; an ON state in which all outlets are enabled (supplied with the AC line voltage); and an automatic state of operation in which 25 the slave outlets 26 are enabled or disabled in response to current flow from the master outlet 24. The power controller 22 also has an input terminal 36 where a low-voltage control signal can be applied in the automatic mode of operation to enable the slave outlets 26 independent of current flow from the master outlet , 24.
The power controller 22 is schematically illustrated in fig. 2.
The master outlet 24 has a neutral terminal 38 that is wired directly to the neutral terrninal 40 of the plug 30. It has a "hot" terminal 42 that is coupled by a switching module 44 and the manual switch 34 to the hot terminal 46 of the plug 30. The slave outlets 26 are essentially wired in parallel with each other.Their neutral terrninals (not specif1cally indicated with reference numerals) are wired directly to the neutral terminal 40 of the plug 30. Their hot terminals are wired together and coupled through the switching module 44 and the manual switch 34 to the hot tcrmin~l 46 of plug 30. To simplify illustration, ground terminals of the plug 30 and the power outlets have not been shown. It will be appreciated that the ground terminal of all power outlets will be wired directlythe ground terminal of the plug 30.
The switching module 44 effectively enables and disables the slave outlets 26 in the automatic mode of operation. It includes a power supply 48 that receives the AC line voltage. It includes a controllable switch 50 that serves to couple the hot terrninals of the slave outlets 26 to the hot terminal 46 of the plug 30. In an open state, the switch S0 isolates the slave outlets 26 from the AC voltage, disabling the slave outlets 26. In a closed state, the AC voltage is applied to the slave outlets 26, enabling them.
The state of the switch 50 is controlled in response to current flow from the master outlet 24. Although presence or absence of current flow can be used to trigger operation of the slave outlets 26, use of current thresholds is preferred. In a typical application, a turn-on threshold of 50 milli~mperes and a turn-off threshold of 20 milli~mperes may be implemented.
More specifically, the switching module 44 has a current detector 52 effectively in series with the master outlet 24. The current detector 52 may be a low-impedance resistive device and diodes may be used to clamp -the AC voltage drop developed across the detector 52. A transformer with its primary in series with the master outlet 24 might be used as part of an alternative current sensing arrangement. The AC voltage drop is applied to an amplifier 54. The amplified voltage signal is received by a rectifier 56. A
5 summer 58 combines the rectified voltage with the optional low-voltage control signal, which will be assumed at present not to be applied to the power controller 22. A capacitive filter 60 effectively removes AC components and other noise, leaving a filtered voltage signal that is proportional to the magnitude of the current flowing from the master outlet 24. A reference source 62 10 provides a reference voltage that might typically be 5 volts. A comparator 64 compares the filtered voltage signal with a reference voltage. When the filtered signal exceeds the reference voltage, the comparator' s output terminal rises to the supply voltage and trips the switch 50 to its closed state through a switch driver 66, enabling the slave outlets 26. The comparator' s output terminal is 15 coupled to the input of the summer 58 to introduce a measure of hysteresis.
When the filtered voltage thereafter drops below a lower switching threshold created by the hysteresis, typically about 2 volts, the comparator's output voltage drops to zero, opening the switch 50. Gain will of course be adjusted such that a current of 50 milliamperes from the master outlet 24, the turn-on 20 threshold, produces a filtered voltage signal of 5 volts and a current of 20 milli~mperes produces a filtered voltage signal of 2 volts. The range of the current detector 52 may be extended with a variable shunt resistor 68. Details of implementation will be readily apparent to those skilled in the electrical arts.
The low-voltage control signal is introduced through an 25 opto-isolator 70. Low voltage DC control of the slave outlets 26 is made conveniently possible by applying the control voltage to the input of the summer 58. It should be apparent that a 5-volt DC signal applied to the input 2~39053 terminal 36 is sufficient to enable the slave outlets 26 and 2-volts DC signal, sufficient to m~int~in their enable state. Reducing the control signal below 2 volts disables the slave outlets 26, assuming a device is not then operating from the control terminal In the arrangement shown in fig. 1, specifically when the manual switch 34 is set for automatic operation, the operating state of the computer 10 determines the operating state of the peripherals. The peripherals will have their ON-OFF switches (not illustrated) left in an ON state. When the computer 10 is turned on, using its ON-OFF switch (not illustrated), it draws operating current from the master outlet 24 that exceeds the turn-on threshold.
The slave outlets 26 are then enabled and the peripherals powered up. When the computer 10 is shut down, once again using its ON-OFF switch, current flow from the master outlet 24 drops to zero, below the turn-off threshold, and the slave outlets 26 are disabled, shutting down the peripherals.
Fig. 3 shows an arrangement in which the computer 10 and peripherals (except the monitor 12) are plugged into the slave outlets 26 of thepower controller 22. These components of the system have their local power switches set to ON. A special call adapter 72 is effectively plugged into the master outlet 24. The purpose of the call adapter 72 is to power up the computersystem in response to an incoming telephone call and to power down the computer system when communication is complete. Since the system operates unattended, the monitor 12 is not required. By plugging the monitor 12 into the master outlet 24, an individual can start-up or shut down the computer system by turning the monitor 12 on or off.
The call adapter 72 is shown in greater detail in the electrical schematic of fig. 4. The call adapter 72 includes a control module 74 that has two phone jacks 76, 78 configured to receive conventional connectors 80, 82 from the system modem 20 and a telephone line. It effectively defines a 21390~3 telephone line segment 84 between the two phone jacks 76, 78 that is tapped to provide signals that trigger enabling and disabling of the slave outlets 26. It comprises a power supply 86 that operates from an internal battery 88 and from a separate power module that is a conventional AC adapter 90. The AC adapter 5 90 incidentally functions as the connector necessary to couple the call adapter 72 to the master outlet 24 to control operation of the slave outlets 26 by drawing appl.~pliate currents.
The call adapter 72 includes an AC load mod~ ting circuit 92.
The load modulating circuit 92 includes a load inlellupler switch 94 that couples the circuit 92 to the AC adapter 90 and llltim~tely to the master power outlet 24.
The load mod~ ting circuit 92 includes a resistive load 96 and a reactive load 98. Switches 100, 102 within the load mod~ ting circuit 92 connect the resistive and reactive loads 96, 98 separately to the AC adapter 90 to vary the current drawn by the AC adapter 90 from the master outlet 24. The resistive 15 load 96 is a relatively low impedance that is momentarily connected to the ACadapter 90 when the slave outlets 26 are to be enabled. Its impedance is simply selected to ensure that a current above the turn-on threshold is drawn from the master outlet 24. The reactive load 98 is a higher impedance, low-loss device that is continually connected to the AC adapter 90 after start-up of the computer 20 system to m~int~in current above the lower turn-off threshold. The objective is to reduce power consumption within the call adapter 72 itself. A single low impedance load is otherwise sufficient.
The battery 88 and the load interrupter switch 94 are provided to ensure that the slave outlets 26 are properly disabled. The inlellupler switch 94 25 is momentarily opened to prevent the call adapter 72 from drawing operating current through the AC adapter 90. In its open state, it effectively isolates both the power supply 86 and the load mod~ ting circuit 92 from the master outlet.
This ensures that current flow from the master outlet 24 drops well below the Z1~9Q53 turn-off threshold. The battery 88 m~int~in~ operation of the call adapter 72 during that brief time. A large capacitor may be substituted as the necessary internal power source during momentary disconnection from the master outlet 24. These features are preferred but are not critical.
S The call adapter 72 includes a ring detection circuit that generates a RING DETECTED signal (a logic high pulse) when a ring signal associated with an incoming call is received. The RING DETECTED signal controls enabling of the slave outlets 26 and powering up of the computer system. In this embodiment, the RING DETECTED signal is not generated unless a preset number of rings are actually sensed in a limited period of time. The object is to avoid powering up the computer system in response to an external communications device that immediately hangs up or when the call is answered by another device on the phone line.
The ring signal is typically a large AC voltage signal on the telephone line. That circuit includes a ring detector 104 that is essentially anAC-coupled envelope follower adapted to produce a triggering signal (a logic high pulse) in response to each ring. The triggering signal resets a ring timer 106 to zero and also increments a ring count m~int~ined by a ring event counter 108. If the ring count is greater than 0, the ring event counter 108 enables thetiming function of the timer 106 (the enabling incidentally restarting the ring timer 106 at zero). The ring timer 106 thus effectively measures the time between successive rings. If the timer 106 times-out, it resets the ring event counter 108, effectively assuming that the calling device has hung up. The time-out period is set simply to exceed the normal period between typical rings in telephone communications, and the ring count consequently reflects the rings of a single incoming call. A programmable logic block 110 compares the ring count with a ring value preset by a system user. The value may typically range between 1 and 8. If the ring value is set to 1, the RING DETECTED signal is produced immf~ tely in response to an incoming call. The RING DETECTED
signal is otherwise produced only when the set number of rings are detected and counted. It should be noted that the programmable logic blocks referred to in 5 this specification use standard jumpers to ground and supply voltages to set binary representations of values. They use standard comparators to compare their reference values with binary values generated by other circuit components.The call adapter 72 includes an on/off-hook detector 112 that produces an OFF-HOOK signal when the modem 20 goes off-hook to answer 10 an incoming call and an ON-HOOK signal when the modem 20 goes on-hook as to discontinue a call. The on/off-hook detector 112 is not entirely conventional. It senses changes in DC current in the telephone line that occur in response to operation of the modem 20. A resistive sensing device 113 is effectively installed in the telephone line. When the modem 20 goes off-hook, 15 the effective DC impedance it presents to the line drops and DC current flow in the line increases dramatically. This produces a corresponding increase in the DC component of the voltage drop across the resistive device 113. When the modem 20 goes on-hook, current flow in the line decreases dramatically producing a corresponding decrease in the DC component of the voltage drop 20 across the resistive device. The voltage changes are converted in a conventional manner into corresponding OFF-HOOK and ON-HOOK Signals (both logic-high pulses). A major advantage of the on/off-hook detector 112 is that itdoes not respond to on-hook and off-hook states of other devices on the telephone side of the jack 78 such as an actual telephone that can also be used to 25 answer incoming calls.
The call adapter 72 tallies any series of closely spaced on-hook events generated with the modem 20. Each ON-HOOK signal increments a hook event counter 114 and also restarts a hook timer 116 at zero. If the count is greater than 0, the hook event counter 114 enables the timing function of thetimer 116 (incidentally restarting the timer 116 at zero). The hook timer 116 thus tallies the time between between successive on-hook events. If the hook timer 116 times-out, it resets the hook event counter 114 to zero. A
programmable logic block 118 compares the hook event count with an on-hook limit that is preset by a system user (typically 1 to 8). It generates an END-OF-SESSION signal (logic-high pulse) if the count matches the preset limit. If the on-hook limit is set to 1, the END-OF-SESSION signal is generated whenever the modem 20 goes on-hook. Otherwise, an END-OF-SESSION signal is not generated unless the modem 20 goes repeatedly on-hook and off-hook within a limited period of time. Such a sequence of on-hook and off-hook events is not natural to telephone communications. The computer 10 can be appropriately programmed to generate such a sequence whenever its has completed a communication session to provide a positive indication that the system should be powered down.
Detecting the first instance in which the modem 20 goes on-hook is sufficient for many applications. However, the arrangement described permits the computer 10 to automate more complex and time-consuming commllnication tasks, such as immediately faxing a document received during a communication session to various destination.
The call adapter 72 includes latches that effectively m~int~in different operating states: IDLE, RING COUNTING, SESSION START-UP, SESSION ACTIVE, and SESSION CLEAN-UP. These are diagrammatically illustrated in fig. 5 together with conditions controlling transitions between states. The latches are a power status latch 120, a start-up status latch 122, and a clean-up status latch 124. The particular designations will become more me~ningful from the description of operation below. These latches are of a conventional type in which the latch is set (Q terminal output set to logic high) 2~3~053 or reset (Q terminal output set to logic low) in response to leading edges of logic-high pulses applied to set and reset tcrmin~ls, respectively. The call adapter 72 also has a session timer 126 that generates a time-out signal (a logic high pulse) for the SESSION START-UP and SESSION CLEAN-UP states.
The session timer 126 has an enable terminal that enables its timing function when set to a logic high and disables the timing function when set to a logic low. A transition from logic high to logic low values also resets the timer 126 to zero. A programmable logic block 127 allows a user to specify the desired time-out period, between 1 and 32 minutes.
In the IDLE state, the computer system is OFF and the call adapter 72 awaits an incoming call. The hook event counter 114 is set to 0 and disabled. The session timer 126 is disabled and set to zero. The ring event counter 108 is set to zero but enabled. The ring timer 106 is disabled and set to zero. The three latches 120, 122, 124 are all reset.
In response to detection of ring signal, the call adapter 72 enters the RING COUNTlNG state. Procedures described above will generate either a time-out from the ring timer 106, returning the call adapter 72 to its IDLE
state, or a RING DETECTED signal if the ring count reaches the predetermined ring count setting.
If the RING DETECTED signal is generated, the call adapter 72 enters its SESSION START-UP state. The RING DETECTED signal closes the switch 100 placing the resistive load 96 in circuit with the AC adapter 90.
This draws a current from the master outlet 24 that exceeds the turn-on threshold and activates the slave outlets 26 and the computer system. The RING DETECTED signal also sets the power status latch 120, which in turn closes the switches 102 and places the reactive load 98 continually in circuit with the AC adapter 90 to m~int~in current flow from the master outlet 24 above 2~390S3 the lower turn-off threshold. It also enables the hook event counter 114. The RING DETECTED signal also sets the start-up status latch 122 and resets the clean-up status latch 124. Setting the start-up status latch 122 in turn disables the ring event counter 108 (incidentally resetting the ring event counter 108 tozero) and enables the session timer 126 through an OR gate 128 shared with the clean-up status latch 124. When the logic-high pulse constituting the RING
DETECTED signal ends, the switch 100 is opened and the resistive load 96 is isolated from the AC adapter 90.
The call adapter 72 remains in the SESSION START-UP mode until the session timer 126 generates a time-out or the on/off-hook detector 112generates an OFF-HOOK signal. If a time-out occurs, the session timer 126 resets the power status latch 120, ultimately disabling the slave outlets 26 andreturning the call adapter 72 to its IDLE state. The sequence of events following such a time-out by the session timer 126 are described in greater detail below with reference to the SESSION CLEAN-UP state.
If the modem 20 goes off-hook before the time-out, the on~ff hook detector 112 generates an OFF-HOOK signal and the call adapter 72 enters its SESSION ACTIVE state. The OFF-HOOK signal is applied to the reset terminal of the start-up status latch 122. Once reset, the start-up status latch 122 disables the session timer 126 and resets its count to zero. The slaveoutlets 26 and the computer system remain powered until an END-OF-SESSION signal is generated in response to the modem 20 going on-hook either once or repeatedly under control of the computer 10.
In response to the END-OF-SESSION signal, the call adapter 72 enters its SESSION CLEAN-UP state. The END-OF-SESSION signal sets the clean-up status latch 124 which in turn enables the session counter.
The call adapter 72 remains in this state until the session timer 126 times-out,allowing the computer system to perform such tasks as may be necessary, for 21390~3 example, recording received data on disk or printing received data on the printer 18).
When the session timer 126 times out, it produces a logic high pulse that resets the power status latch 120 and simultaneously opens the load in~ up~er switch 94. Operating current is momentarily drawn from the battery 88, and current demand from the AC adapter 90 and thus the master outlet 24 drops below the turn-off threshold. This disables the slave outlets 26 and shutsdown the computer system. Resetting the power status latch 120 enables and resets the hook event counter 114 and also resets the start-up status latch 122 and the clean-up status latch 124 through inverted reset terminals (resetting inresponse to logic lows) of the latches 122, 124. With the two latches 122, 124 reset, the session timer 126 is then zeroed and disabled. Resetting the start-upstatus latch 122 also causes the ring event counter 108 to be enabled. The call adapter 72 is once again in its IDLE state.
Fig. 6 shows diagrammatically how the call adapter 72 can be integrated into a modem 130. The control module 74 is installed together with modem circuitry 134 within the modem's housing 132. The phone jack 78 is now mounted on the housing 132 to permit connection to a telephone line. The other phone jack 76 is elimin~te~l and the control module 74 is wired directly to the modem circuitry 134. The power supply 86 of the control module 74 provides low voltage DC to the modem circuitry 134 along a supply line 136, elimin~ting the need for two separate supplies. The turn-on threshold of the power controller 22 may be increased, if necessary, to reflect the increased operating current attributable to the modem 130. An alternative approach is to modify the modem's control software to incorporate the control functions of the call adapter 72. The modem 130 will normally be configured for ring detection and for response to on-hook and off-hook control signals tr~n~mitted by the computer 10, instructing the modem to go on-hook and off-hook. Such control signals, rather than changes in current level in the telephone line, may serve as triggering signals for disabling of the slave outlets 26. The load mocl~ ting circuit 92 and the battery-operated power supply 86 (assuming an interrupter switch 94 is desired) is incorporated, ~prupliately adapted to reflect operating5 current requirements of the modem.
Fig. 7 diagrammatically illustrates a computer 138, a printer 140 and a serial adapter 142 in a serial I/O cable 144 between the computer 138 and the printer 140. The computer 138 is connected to an electric main and is powered. The serial adapter 142 includes the AC adapter 90, described above, 10 which is plugged into the master outlet 24 of the power controller 22. The printer 140 is plugged into one of the slave outlets 26 and its local ON-OFF
switches (not illustrated) is left continually in an ON state. In this configuration, the serial adapter 142 essentially powers up and shuts down the printer 140 in response to the computer's requirements.
The serial adapter 142 has two operating modes. In mode 1, the serial adapter 142 shuts down the printer 140 in response to lack of activity onthe cable 144. In mode 2, the serial adapter 142 shuts down the printer 140 in response to a shut-down sequence placed on the control lines. The shut-down sequence will typically be a unique code that does not occur on the control lines 20 in normal operation. For mode 2 operation, the computer 138 must be programmed to generate the shut-down sequence on appropriate control lines.
Software may be provided, for example, that presents a menu allowing a user to select peripherals to be shut down. In response to the user selection, shut-down sequences may be tr~nsmitted to appropriate serial adapters 25 controlling the operation of the selected peripherals. A mode setting block 146 permits a user to specify whether mode 1 or mode 2 operation is desired. The output terminal of the mode selection block is at a logic high if mode 1 is Z~390S3 selected and at logic low if mode 2 is selected.
The configuration of the serial adapter 142 is apparent in fig. 8.
Components common to the call adapter 72 have been indicated with like reference numerals and will not be described in detail. The serial adapter 142 has standard RS232 connectors 148, 150 that mates with complementary connectors 152, 154 of the computer 138 and printer 140. It defines a I/O line segment 156 between the two connectors 148, 150 that is tapped. A
programmable logic block 158 connected to the taps allows a user to select signal lines of the cable 144 that are to be monitored. This is done with jumpers connected to the taps.
A control signal level detector 160 is connected by the programmable logic block 158 to a printer 140 control line. The printer 140 control line might typically be set to a logic high (alternatively a logic low) when the computer 138 asserts the line to communicate with the printer 140. The control signal level detector 160 is simply adapted to respond to the logic high(alternatively logic low) of the printer 140 control line by producing a logic-high CONTROL DETECTED signal.
A data signal detector 162 is connected to all data lines of the cable 144. It simply senses logic state transitions on the data lines and generates a DATA DETECTED signal which is essentially a logic-high pulse.
While the data lines are active, the data signal detector 162 will tend to produce a stream of DATA DETECTED signal pulses.
The output terminals of the control signal level detector 160 and the data signal detector 162 are connected to input terminals of an OR gate 164.The OR gate 164 produces a CHANNEL ACTIVITY signal which is a logic high whenever the control or data lines are active.
A shut~own sequence detector 166 responds to tr~n.~mi~ion of the shut-down sequence along control lines of the cable 144. It comprises a 2~39053 conventional shift register with 8 or more bits. One control line, in this instance the DTR ("data terminal ready") is used as a clock to shift data bits into the register. Another control line, in this instance RTS ("ready terminal send") provides input data to the register. Each time the DTR line is asserted, the logical state of the RTS line is shifted into the register. If the bits of the register match a predetermined shut-down sequence stored by the shut-down sequence detector 166, the detector 166 produces an END-OF-SESSION signal (a logical high pulse) at its output terminal, indicated with "match" in fig. 8. If the mode setting block 146 is set to a mode 1, the reset terminal of the shut-down sequence detector 166 is at a logical high (the resets illustrated are ORed internally) the shut-down sequence detector 166 is disabled and its match terminal is set low. If mode 2 is specified, the mode setting block 146 no longer suppresses operation of the shut-down sequence detector 166.
A mode switch 168 couples the enable terminal of the session timer 126 to either the output of a timer status latch 170 or through an inverter 172 to the output of the OR gate 164. The mode switch 168 is controlled by the mode setting block 146. If the mode setting block 146 is set for mode 1, the session timer 126 is coupled to the OR gate 164. It can then be disabled and restarted by the CHANNEL ACTIVITY signal. If the mode setting block 146 is set for mode 2, the session timer 126 is coupled to the timer status latch 170.
Is then set when the timer status latch 170 is set and disabled and restarted when the timer status latch 170 is reset.
The serial adapter 142 has four states: IDLE, SESSION
ACTIVE, EOS ("end of session") DETECTION, and SESSION CLEAN-UP.
These are diagrammatically indicated in fig. 9. The EOS DETECTION state occurs only in mode 2 operation.
Mode 1 operation will now be described. In the IDLE state, the power status latch 120 of the serial adapter 142 is reset. The shut-down 213~0~3 -sequence detector 166 is disabled by the mode setting block 146 and remains disabled throughout subsequent stages. The timer status latch 170 is reset but its state does not affect operations at any subsequent adapter state. Although the enable terminal of the session counter is set to a logic high, the session timer126 is time-out and inoperative.
If a CHANNEL ACTIVITY signal is generated, the serial adapter 142 enters its SESSION ACTIVE state. The CHANNEL ACTIVITY
signal sets the power status latch 120 which then couples the load motllllating circuit 92 to the AC adapter 90 and enables the slave outlets 26, as described with reference to the call adapter 72 above. It should be noted that the switch 100 associated with the resistive load 96 is now triggered from the power statuslatch 120 through an edge detector 174. The CHANNEL ACTIVITY signal tends to be generated repeatedly by data transfers on the cable 144. It repeatedly enables and disables the session timer 126 through the inverter 172 and the mode switch 168. This effectively suppresses timer operation and no time-out occurs.
If the control signals are negated and no data activity occurs, the serial adapter 142 enters its SESSION CLEAN-UP state. In absence of the CHANNEL ACTIVITY signal, the timer 126 remains enabled and times its preset time-out period. It then generates its time-out signal, a logic high pulse, which resets the power status latch 120 and temporarily opens the load interrupter switch 94. The slave outlets 26 are thus disabled and the printer 140 is shut down. The serial adapter 142 is once again in its IDLE state.
In Mode 2 operation, the IDLE state is similar but the session timer 126 is positively disabled by the timer status latch 170 and the mode setting block 146 no longer disables the shut-down sequence detector 166 by holding a reset terrninal of the shut-down sequence detector 166 high. In 21390~3 -response to activity on either the control or data lines, the serial adapter 142once again enters its SESSION ACTIVE state and remains in that state while the activity continues. The shut-down sequence detector 166 is repeatedly reset by the data signal detector 162 suppressing detection of sequences on the control lines.
If activity on the data lines ceases, the serial adapter 142 enters the EOS DETECTION state. The computer 138 can clock the shut-down sequence into the shut-down sequence detector 166 over the control lines.
Once the sequence is detected, the shut-down sequence detector 166 generates its END-OF-SESSION signal, the session timer 126 is enabled, and the serial adapter 142 enters its SESSION CLEAN-UP state.
During EOS DETECTION, the serial adapter 142 returns to the SESSION ACTIVE state if data is transferred on the data lines. The resulting DATA DETECTED signal resets the shut-down sequence detector 166.
Although control signals alone can generate a CHANNEL ACTIVE signal, it will be noted that only data activities reset the shut-down sequence detector 166. Thus, tr~n~mitting the shut~own sequence along the control lines does not force a return to the SESSION ACTIVE state.
During SESSION CLEAN-UP, the session timer 126 times-out, resetting the power status latch 120, disabling the slave outlets 26 and shlltting down the printer 140. Resetting of the power status latch 120 resets the timer status latch 170. The serial adapter 142 is then back to its IDLE
state.
If during SESSION CLEAN-UP either a control line is asserted or data is transferred, a CHANNEL ACTIVE signal is generated. This resets the timer status latch 170 and disables the session timer 126, returning the serial adapter 142 to its SESSION ACTIVE STATE. A control line is apt to be asserted, for example, if the computer 138 is required to process a new print 213~05~3 job.
The serial adapter includes a programmable block 176 for supplying power via serial cable to a mouse (not shown). The block 176 comprises conventional jumpers that tap into the control lines of the line segment 156 that normally supply power to a mouse. The jumpers are in turn connected to the power supply to derive the necessary driving voltage. Signals generated by operation of the mouse can be detected on the component lines of the segment 156 by applopliate configuration of the progr~mming block 158.
Operation of the mouse can be used to power up other equipment.
Additional steps must be taken to configure the adapters 72, 142 to power up MacIntoshTM computers. The ON-OFF switches of such computers are typically left in an ON state. Power up is often initiated by depressing a particular key on the computer' s keyboard. This has the effect of shorting certain lines in the Apple Desktop Bus (ADB) TM and initiating start-up.
Each of the adapters 72, 174 may operate with such computers if provided with a connector that fits into the ADB ports of the computer and engages the pertinent lines of the bus. The output terminal of its power status latches may be connected to a switch that shorts the relevant lines through the additional connector when the latch is set to enable the slave outlets.
It will be appreciated that a particular embodiment of the invention has been described and that modifications may be made therein without departing from the spirit of the invention or necessarily departing fromthe scope of the appended claims. In particular, it should be noted that the various procedures embodied by the invention have been shown implemented in hard-wired form. It will be readily apparent that various control functions suchas timing, value comparison, and detection of digital signal on I/O lines can beimplemented with a microprocessor and appLopliate software code. The state diagrams presented may serve as a guide for such software implementations.